Sessile drops can be present in a variety of material systems, and the shapes of the sessile drops can affect the performance characteristics of such systems. The shape of a sessile drop can also characterize the properties of a surface on which the drop is disposed. For example, in the case of a wetting system, the wettability of a surface can be characterized by the wetting contact angle of the drop.
One typical approach to measuring the shape of a sessile drop employs lateral measurement and/or visual inspection of the drop. Some contact angle goniometer systems, for instance, use an optical subsystem to create a visual representation of the sessile drop from the side. The image is then used to measure the wetting contact angle by visual inspection. Unfortunately, such approaches based on lateral measurement and/or visual inspection are inherently limited. In particular, techniques based on lateral measurement and/or visual inspection often cannot be used to determine the shape of a sessile drop having a small drop diameter, and/or in situations wherein an optical path from the measurement instrument to the profile of the sessile drop is obstructed. Therefore, there exists a need for improved methods of determining the shape of a sessile drop.